There are several sites for monitor calibration.
The process is always the same:
With an image made of a scale of grays (usually there are 7 different levels in the image) you have to adjust the contrast in order to distinguish the two lowest levels of gray (black and very dark gray).
Than adjust the brightness to achieve the same effect for the highest levels (white and very bright gray).
For the color it's more a matter of personal taste, because a real calibration needs an external device...
If you have a dvd player on your pc and a dvd with a THX standard (Star Wars for example) there is a step by step guide in the language menu.
Actually THX is a standard for calibration of video and audio for obtaining the best quality from any movie.
Be warned that this calibration is for CRT and not for LCD monitors... With LCD you could have to adjust the controls a bit (my lcd, with THX is a bit too bright...)